I think bid shopping is dirty pool. I never do it. I've had cheeseball clients and GCs tell me "I've got a bid for $64,000 or whatever, if you can beat that by 5% the job is yours." Nope. Good luck with that.
I had one GC we did work for 3-4 years ago on a couple jobs. Clean, on the up and up. We did well, he did well. Then we start getting phone calls like "this is yours if you can do it for $X." Have to pass, sorry.
Well for the next year we didn't win a thing. It got to the point where we stopped bidding. When we did, I got a call from their estimator saying "I need your number." No, man, we never get work, it's a pointless exercise. "But I always go in with your number." So why don't I ever get work? "I don't handle the subs or the projects." Click.
Couple months later I get a call from the owner. "We really want to start a relationship back up with you." Ok, so we start bidding again, but this time I make it a point to be late enough so to not have my number count in their number. Get a call. "We got the job, but we went in with a guy who had a lower number." Good for you. Stick with them, I think they'll work out for you better than we will.
Almost a year later we get a call again from the owner. "Come on, my friend, bid some work, let's see if we can do something together." I'm bored and feeling a little punchy, so I set up a meeting. I say we've been bidding off and on for 3 years, and we haven't seen an ounce of work. "But your prices are higher than the guy we use." So, use him for crying out loud, he's been beating me for almost 3 years. "He just went bankrupt, and we need to find someone else."
But here is an example of bid shopping at its worst:
There is a large fortune 500 chemical company (sponsors a NASCAR Sprint Cup team) that has elevated bid shopping into an art form. They get 4 or 5 contractors qualified at their sites, and for each project, they set up a reverse auction for the work. You get set up with an on-line account, and on the day of the auction, you go on line for an hour to work the process. You enter your first bid, and if it's higher than the opening price that they set - THEY set - you get a message that "your initial bid is too high, please try again." The crafty part is that you don't see anyone else's number or identity, just the messages "you are not the low bidder" or "your initial bid is too high, please try again."
I did work for them a few years ago this way, but I just got sick of it. The last time I did it, I logged in and went to enter my initial number, and got the "your initial bid is too high" crap. I immediately logged off and went for an early lunch. I'm driving down the road and I got a call from the auction administrator who said "we see you logged in and entered your first number, but then you logged out, we were looking forward to a bid from you." I told them you got my bid, but your computer program told me I was too high, so, I wish you the best, keep us in mind.